Method and system for detecting position of a vehicle relative to tracks the vehicle is running on

ABSTRACT

A vehicle for an automated storage and retrieval system is configured to follow a set route on a track being laid out in the automated storage and retrieval system and having one or more track features. The vehicle includes a first set of wheels capable of moving the vehicle in a first direction; a second set of wheels capable of moving the vehicle in a second direction perpendicular to the first direction; and a plurality of sensors attached to the vehicle and configured to detect track features and to measure a distance to a track feature while the vehicle is moving in the first direction or the second direction.

BACKGROUND

A remotely operated vehicle or robot for picking up storage bins from astorage system is known. A detailed description of a relevant prior artstorage system is presented in EP1037828B1, and details of a prior artvehicle being suitable for such a storage system is disclosed in detailin Norwegian patent NO317366B1 and WO2015193278A1. Such prior artstorage systems comprise a three-dimensional storage grid containingstorage bins that are stacked on top of each other up to a certainheight. The storage grid is normally constructed as aluminium columnsinterconnected by top rails or tracks, onto which a plurality ofremotely operated vehicles, or robots, are arranged to move laterally.Each vehicle is equipped with motors for moving the vehicle from oneposition to another and for driving a lift device adapted for pickingup, carrying, and placing bins that are stored in the storage grid. Apower supply is supplying power to the motors and drivers comprised inthe vehicle, e.g. a rechargeable battery. The vehicle typicallycommunicates with a control system via a wireless link and can berecharged at a charging station when needed.

Rotation of the wheels may be driven by belts connected to the wheels orby individual driving means situated at or at least partly within thewheels. The last example will provide a responsive robot with highcontrol of acceleration and deceleration between a start and a stopposition.

When a robot is moving on the tracks, it is controlled to acceleratefrom a start position and decelerate to a stop position. The start andstop positions will depend on the route set up for a robot prior topicking up a bin from one storage column in the storage grid and placingit in another storage column. A set route of a robot will typicallycomprise several start and stop positions. A route for a specific robotwill be set up by a supervisory system having control of all storagebins and their content as well as the positions of the vehicles handlingthe bins.

When operating and controlling a robot following a set route relative totracks laid out on a frame structure forming a grid, it is vital toalways keep track of all operating robots and their positions. Thepositions of a robot can be acquired in different ways. One way is totrack the position of the robot relative to the tracks on top of theframe structure. The position can be acquired by means of trackingdevices located externally to the robot or by devices integrated in therobot.

JP H03 290712A describes a method for tracking position of a remotelyoperated trackless vehicle following a set route relative to inductionguide paths laid out as floor tiles forming a frame structure. Thevehicle has integrated sensors for detecting crossings of the guidepaths along a route. Signals are transmitted to a controller forcontrolling the vehicle according to number of crossings passed.

By using integrated tracking devices, the robot itself will be able tokeep track of its position. Integrated tracking devices are howeverquite complex systems and not necessarily very precise.

There is a need for a simple yet precise way of detecting the positionof a robot running on tracks, relative to a frame structure.

According to embodiments of the present invention, the position of therobot is detected by integrated tracking devices tracking the number ofcrossings passed in x- and y-directions relative to tracks laid out as agrid structure as well as detecting distance to the next track crossing.

SUMMARY

In one aspect, embodiments disclosed herein are defined by a method fortracking the position of a remotely operated vehicle following a setroute relative to tracks laid out on a frame structure forming a storagegrid, the vehicle having first and second sets of wheels connected todrives for moving the vehicle in corresponding x- and y-directions onthe grid, comprising:

-   -   receiving information of a total number of track crossings to        pass between start and stop positions in x- and y-directions        according to the set route;    -   directing sensors attached to the vehicle at the tracks along        the route of the vehicle, characterized in that    -   at least a first sensor is attached to a wheel support on one        side of the vehicle, in the x-direction, and a second sensor is        attached to a wheel support on the other side of the vehicle, in        the y-direction, and    -   detecting and monitoring track crossings passed when moving the        vehicle in the x- and y-directions according to the set route by        means of wheel supports that are active, enabling contact        between wheels and tracks, where the sensors attached to the        active wheel supports, are arranged for detecting the track        crossings, and the sensors attached to passive wheel supports,        are arranged for measuring distance to next track crossing;    -   transmitting a signal to a controller, controlling the drives of        the wheels of the vehicle, when the number of track crossings        passed is close to the total number of track crossings to pass        between the start and stop positions in respective x- and        y-directions along the set route.

Further features of the method are defined in the dependent claims.

In one aspect, embodiments disclosed herein are also defined by aremotely operated vehicle for tracking the position of the vehiclefollowing a set route relative to tracks laid out on a frame structureforming a storage grid, the vehicle having first and seconds sets ofwheels connected to drives for moving the vehicle in corresponding x-and y-directions on the grid, said vehicle comprises:

-   -   means for receiving information of number of track crossings to        pass between start and stop positions in x- and y-directions        according to the set route,    -   sensors attached to the vehicle and directed at the tracks along        the route of the vehicle, characterized in that at least a first        sensor is attached to a wheel support on one side of the        vehicle, in the x-direction, and a second sensor is attached to        a wheel support on the other side of the vehicle, in the        y-direction, and further comprising:    -   means for detecting and monitoring track crossings passed when        moving the vehicle in the x- and y-directions according to the        set route by means of wheel supports that are active, enabling        contact between wheels and tracks, where the sensors attached to        the active wheel supports are arranged for detecting the track        crossings, and the sensors attached to passive wheel supports,        are arranged for measuring distance to next track crossing;    -   controller for controlling the drives of the wheels of the        vehicle when the number of track crossings passed is close to        the total number of track crossings to pass between the start        and stop positions in respective x- and y-directions along the        set route.

In one embodiment, the at least first and/or second sensors are opticalsensors.

Other aspects and advantages of the claimed subject matter will beapparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention will now be described with reference to thefigures, where:

FIG. 1 shows a robot equipped with sensors according to an embodiment ofthe invention;

FIG. 2 illustrates how light is reflected from the grid;

FIG. 3 illustrates the principle of using track sensors for detectingthe position of a robot relative to tracks, and

FIG. 4 shows light sensor signals are generated when moving a robot inx- and y-directions of a grid structure.

DETAILED DESCRIPTION

In one aspect, embodiments disclosed herein comprise a remotely operatedvehicle, hereafter called robot, for tracking the position of the robotfollowing a set route relative to tracks laid out on a frame structureforming a grid.

FIG. 1 shows an example, in perspective view, of such a robot. The robothaving first and second sets of wheels connected to drives for movingthe robot in corresponding different direction on the grid. The firstand second set of wheels are oriented perpendicular to each other. Forthe sake of clarity, a Cartesian coordinate system is shown with its x-and y-axes aligned along the principal directions of the rectangularvehicle body.

The robot further comprises means for receiving instructions withinformation of the number of track crossings to pass between start andstop positions in x- and y-directions according to the set route.

Sensors are attached to the robot and directed at the tracks along theroute of the robot. In one embodiment of the invention, the sensors areoptical sensors detecting reflection of light from the tracks.

FIG. 2 illustrates the principle of using optical sensors as tracksensors for detecting the position of a robot relative to tracks andgrid structure. Light is reflected from tracks when a robot is movingalong the tracks in x- or y-directions. When the robot is passing atrack crossing, the reflected intensity of the detected light willchange.

In one embodiment of the invention, at least one sensor is attached toone side, running in the x-direction of the robot, and another sensor isattached to the other side, running in the y-direction of the robot.This means that at least one sensor can be active when the robot ismoving in either of the x- and y-directions.

In one embodiment of the invention, the sensors are connected towheel-supports located at each side of the robot. A wheel support willtypically hold two wheels, as illustrated in FIG. 1. Active wheelsupports enable contact between wheels and tracks. Pair of wheelsupports on opposite sides of the robot are active at the same time whenthey are lowered from the body of the robot into the tracks.

In one embodiment of the invention, optical sensors are used. Other oradditional sensors for detecting position of the robot relative to thetracks may also be used, e.g., acoustic sensors. A combination ofdifferent types of sensors is feasible.

The remotely operated vehicle further comprises detecting and monitoringmeans connected to the sensors. This will enable monitoring of trackcrossings passed when moving the vehicle in the x- and y-directionsaccording to the set route.

The vehicle further comprises a controller for controlling the drives ofthe vehicle according to the number of track crossings passed. When thisis close to the total number of track crossings to pass between thestart and stop positions in respective x- and y-directions along the setroute, the controller will initiate deceleration of the robot.

In one aspect, embodiments disclosed herein further comprise a methodfor tracking the position of a remotely operated vehicle or robotfollowing a set route relative to tracks laid out on a frame structureforming a grid. The vehicle having first and second sets of wheelsconnected to drives for moving the vehicle in corresponding x- andy-directions on the grid. The method comprises several steps.

The first step is receiving information of the number of track crossingsto pass between start and stop positions in x- and y-directionsaccording to the set route. This information is passed to the controllerof the remote operated vehicle.

The next step is directing sensors attached to the vehicle at the tracksalong the route of the vehicle. This is described above and illustratedin FIG. 2.

One embodiment comprises attaching at least one sensor to one side ofthe robot, i.e. in the x-direction of the robot, and attaching anothersensor to the other side, i.e. in the y-direction of the robot, where x-and y-directions of the robot correspond to the x- and y-directions ofthe grid structure of tracks the robot is moving on.

Another embodiment of the method comprises attaching at least one sensorto a wheel support. By doing this a sensor will be lowered into thetrack section and will be closer to the track it is directed at when thewheel support it is connected to is active, i.e., contact between wheelsand tracks is established.

When a robot is moving along the tracks it will pass one or morecrossings on its way from a start position to a stop position.

FIG. 3 illustrates this principle where a robot equipped with a lightsensor receives reflected light from the track. When the robot is movingthrough a track crossing, the intensity of the light reflected will dropsince no light is reflected.

The next step of an embodiment of the invention is detecting andmonitoring track crossings passed when moving the vehicle in the x- andy-directions according to the set route. Detection of track crossings isbased on measured intensity of reflected light. If other types ofsensors are used, the detection is based on detection of change inreceived signal.

FIG. 4 shows light sensor signals generated when moving a robot in x-and y-directions of tracks laid out as a grid structure. Based on thesensor signals, the robot is able to keep track on the number of trackcrossings passed.

FIG. 4A shows an example of a track crossing, where there are doubletracks in the x-direction, and single tracks in the y-direction. A robotrunning in the x-direction will have sensors directed in they-direction, ref. FIG. 3. It will thus detect the single-trackconfiguration. When the robot is running in the y-direction it willdetect the double track configuration. The letters B and C in FIG. 4Aare referring to corresponding signals shown in FIGS. 4B and 4C.

FIG. 4B shows light intensity (I) versus time (t) when a robot isrunning in the y-direction shown in FIG. 4A. As shown in the figure thelight intensity will be high if the sensor receives a strong reflectedsignal from the track it is directed at. When the sensor is passing thetrack crossing, the signal will drop since a reflected signal is absent.A temporary peak of the intensity of the reflected light will occur dueto the double track configuration. After passing the track crossing, theintensity, I, of the reflected signal will become high again until nexttrack crossing.

FIG. 4C shows a similar reflected signal as shown in 4B, but with onlyone drop in the detected signal due to the single-track configuration.

The last step of this embodiment of the invention is transmitting asignal to a controller, controlling the drives of the wheels of therobot when the number of track crossings passed is close to the totalnumber of track crossings to pass between the start and stop positionsin respective x- and y-directions along the set route.

In this way, the controller can control precise deceleration of therobot prior to the next crossing where it is to change direction.

One embodiment of the invention comprises arranging sensors placed onactive wheel supports comprising the sets of wheels for detecting trackcrossings as described above, as well as arranging sensors on passivewheel supports for measuring distance to next track crossing. This canbe used for providing an early warning signal, telling the controllerthat the next track crossing is approaching.

According to one embodiment of the invention, the signal transmitted tothe controller can be used for performing precise control ofdeceleration and acceleration of the vehicle for following a set routealong x- and y-directions.

The following describes an example of how the inventive method can beimplemented on the remotely operated vehicle described above.

The tracks laid out on a frame structure forming a grid can be addressedsimilar as the cells in a spreadsheet. If for instance a storage gridcomprises 100 columns or cells for storing bins, each cell can be givena unique identity. A grid with 10 cells in the x-direction and 10 cellsin the y-direction will make a 2-dimensional track configuration runningon top of 100 cells.

When the movements of the robot are controlled, a controller will keeptrack of which cell the robot is to pick up a bin from, and which cellto place a bin in. Based on this, the controller will set up a route therobot is to follow.

If, for instance, the robot is to pick up a bin from cell C2, and placeit in cell H8, and cells C8 and H2 are blocked by other robots, thefollowing route may be set up by the controller. First leg of the routeis from C2 to C5, the next leg is from C5 to H5, and the last leg isfrom H5 to H8. According to said route, the robot must start and stopthree times. It will first drive in the y-direction, then thex-direction, and finally in the y-direction. The robot will receive thenumber of track crossings to pass between each start and stop positionaccording to said route.

The sensors attached to the robot and detecting means comprised in therobot will detect the number of track crossings passed in eachdirection. When the number of passed crossings is close to the totalnumber of track crossings to pass on each leg, a signal is transmittedto the controller controlling the movements of the robot. In this way,the controller will know exactly when deceleration should start, as wellas the rate and duration of acceleration.

According to embodiments of the present invention, the position of therobot is detected by integrated tracking devices for detecting thenumber of crossings passed in x- and y-directions relative to the trackslaid out as a grid structure is tracked.

The features of the invention can be used in addition to other distancemeasuring means comprised in the robot or in external means.

This method according to embodiments of the invention will provide asimple yet precise way of detecting the position of a robot relative toa frame structure. This enables fast and efficient movements of robotsmoving on tracks laid out on top of the frame structure.

Although only a few example embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications are possible in the example embodiments without materiallydeparting from this invention. Accordingly, all such modifications areintended to be included within the scope of this disclosure as definedin the following claims.

What is claimed is:
 1. A vehicle for an automated storage and retrievalsystem, wherein the vehicle is configured to follow a set route on atrack being laid out in the automated storage and retrieval system andhaving one or more track features, wherein the vehicle comprises: afirst set of wheels capable of moving the vehicle in a first direction;a second set of wheels capable of moving the vehicle in a seconddirection perpendicular to the first direction; and a plurality ofsensors attached to the vehicle and configured to detect track featuresand to measure a distance to a track feature while the vehicle is movingin the first direction or the second direction.
 2. The vehicle accordingto claim 1, wherein at least two of the plurality of sensors areconfigured to detect and/or measure in different directions while thevehicle is moving in the first direction or the second direction.
 3. Thevehicle according to claim 1, wherein at least one of the plurality ofsensors is configured to detect track features and to measure a distanceto a track feature.
 4. The vehicle according to claim 3, wherein atleast one of the plurality of sensors is configured to detect trackfeatures while the vehicle is moving in the first direction andconfigured to measure a distance to a track feature while the vehicle ismoving in the second direction.
 5. The vehicle according to claim 4,wherein at least one of the plurality of sensors is configured to detecttrack features while the vehicle is moving in the second direction andconfigured to measure a distance to a track feature while the vehicle ismoving in the first direction.
 6. The vehicle according to claim 3,wherein at least one of the plurality of sensors is configured to detecttrack features and measure a distance to a track feature while thevehicle is moving in the first direction.
 7. The vehicle according toclaim 6, wherein at least one of the plurality of sensors is configuredto detect track features and measure a distance to a track feature whilethe vehicle is moving in the second direction.
 8. The vehicle accordingto claim 1, wherein at least one of the plurality of sensors is anoptical sensor.
 9. The vehicle according to claim 1, wherein the vehiclefurther comprises: a receiver configured to receive a total number oftrack features between a start position and a stop position of a setroute; drives configured to drive the first set of wheels and the secondset of wheels; and a controller configured to control the drives basedon a number of track features detected and/or a distance to a trackfeature measured by at least one of the plurality of sensors.
 10. Thevehicle according to claim 1, wherein the vehicle further comprises afirst wheel support for supporting the first set of wheels, wherein atleast one of the plurality of sensors is attached to the first wheelsupport.
 11. The vehicle according to claim 10, wherein the vehiclefurther comprises a second wheel support for supporting the second setof wheels, wherein at least one of the plurality of sensors is attachedto the second wheel support.
 12. The vehicle according to claim 11,wherein at least the first wheel support is operable between an activestate in which the first set of wheels are engaged with the track and apassive state in which the first set of wheels are disengaged from thetrack so to engage the second set of wheels with the track.
 13. Thevehicle according to claim 12, wherein the at least one sensor attachedto the first wheel support is configured to detect track features whenthe first wheel support is in the active state, wherein the at least onesensor attached to the first wheel support is configured to measure adistance to a track feature when the first wheel support is in thepassive state.
 14. The vehicle according to claim 1, wherein at leastone of the track features is a track crossing.
 15. A method for trackinga position of a vehicle following a set route on a track being laid outin an automated storage and retrieval system and having one or moretrack features, wherein the vehicle comprises: a first set of wheelscapable of moving the vehicle in a first direction; a second set ofwheels capable of moving the vehicle in a second direction perpendicularto the first direction; and a plurality of sensors attached to thevehicle and configured to detect track features and to measure adistance to a track feature while the vehicle is moving in the firstdirection or the second direction; wherein the method comprises: movingthe vehicle in the first direction or the second direction while:detecting track features by at least one of the plurality of sensors;and measuring a distance to a track feature by at least one of theplurality of sensors.
 16. The method according to claim 15, wherein themethod further comprises: determining a position of the vehicle based ona number of track features detected by at least one of the plurality ofsensors.
 17. The method according to claim 16, wherein the vehiclefurther comprises: a receiver; drives configured to drive the first setof wheels and the second set of wheels; and a controller configured tocontrol the drives; wherein the method further comprises: receiving atotal number of track features between a start position and a stopposition of a set route; and controlling the drives of the first set ofwheels and the second set of wheels based on the total number of trackfeatures and a number of track features detected by at least one of theplurality of sensors.
 18. The method according to claim 17, wherein themethod further comprises the step of: controlling the drives of thefirst set of wheels and the second set of wheels based on a distance toa track feature measured by at least one of the plurality of sensors.19. The method according to claim 15, wherein at least one of theplurality of sensors is an optical sensor, wherein the method furthercomprises optically detecting the track features and/or opticallymeasuring a distance to a track feature.
 20. The method according toclaim 15, wherein the vehicle further comprises: a first wheel supportfor supporting the first set of wheels; and a second wheel support forsupporting the second set of wheels; wherein the method furthercomprises: operating the first wheel support to engage the first set ofwheels with the track, such that the vehicle can move in the firstdirection; and operating the first wheel support to disengage the firstset of wheels from the track so to engage the second set of wheels withthe track, such that the vehicle can move in the second direction.